Added units to the list in maintainers.txt

[SVN r46541]

libs/maintainers.txt

@@ -77,6 +77,7 @@ tr1                   John Maddock <john -at- johnmaddock.co.uk>
 tuple                 Jaakko Jarvi <jarvi -at- cs.tamu.edu>
 type_traits           John Maddock <john -at- johnmaddock.co.uk>
 typeof                Arkadiy Vertleyb <vertleyb -at- hotmail.com>, Peder Holt <peder.holt -at- gmail.com>
+units                 Matthias Schabel <boost -at- schabel-family.org>, Steven Watanabe <steven -at- providere-consulting.com>
 unordered             Daniel James <daniel_james -at- fmail.co.uk>
 utility
 utility/enable_if     Jaakko Jarvi <jarvi -at- cs.tamu.edu>, Jeremiah Willcock <jewillco -at- osl.iu.edu>